Suggestions on LED layout, Biocube 29

So I'm about at the place to start buying LEDs... but I need to figure out this layout issue so I know how many of which to buy. I'm currently thinking 20 LEDs, which should provide a rather large increase in light from my PCs. I wasn't sure if I should alternate every other, or if I could get away with 12 royal blue Crees (3W) and 8 of the Cree XL-Ms. I'm planning on no optics to help the light spread and to help fit into the Biocube 29 hood. I'm wondering if either of these will provide enough blending so I don't end up with stripes of different colored light. I had also debated something like:
XOXOX
XOXOX
XOXOX
XOXOX
where the X's would be royal blues and the Os would be XL-Ms, but I wasn't sure how that would go.
OXXXO
XOXOX
XOXOX
OXXXO
is the other plan I had thought about (that I have pictured in the attachments).

I currently have a rig built that is 12" long and 9" wide. There are 4 strips (U-channel on the back) that are 12" long. I can provide pics of that if needed.

 

Alternating is better, therefore I like your second pattern over the first.

Wait, I just realized your text and pictures don't match.

In the text, the second is preferable. In the pictures, the first is preferable.

 

One of the other reasons I have it set that way is because supposedly, a 2:1 (RB:W) ratio tends to work better (I guess a 1:1 leads to "too much" white, so it has to be dimmed more than the RB). I was at a 3:2 RB:W ratio with the above

 

First one I think would end up looking weird but I dunno about the second one either. Would drolly look better the first though. Is that the amount of less you have to work with?

Sent from my DROIDX using Tapatalk

 

I can make it 24 if I have to... But if I could make it happen with 20 LEDs, I'd prefer to go that route.

 

Are you DIYing or retrofitting with something like a stunner strip?
IMO 2nd option (1st pic) would give better spread.

 

Here's what I've built:

 

bump... more assistance needed

 

Your second LED schematic looks better.

For your heatsinks, why not connect the 4 heatsinks at the ends with 90 degree angle bars (or "L" shaped) on each side so then you wont have the bar midway through the heatsink--not a big deal just a thought.

 

I have it the way it is so that the LEDs can be mounted further to the sides. I suppose I could've mounted to the side of the U-channel.... but an aluminum strip riveted to the channels just seemed easiest to me. Which design are you liking more? The alternating every other, or the one that looks more like an X (with whites)